530 — . Royal Society :— 
the seed, it may be observed that, from the constancy of the amount 
of combined nitrogen present in relation to that supplied, throughout 
the experiments, it may be inferred, as well that there was no evolu- 
tion of free nitrogen by the growing plant, as that there was no 
assimilation of it; but it cannot hence be concluded that there would 
be no such evolution if an excess of combined nitrogen were supplied. 
The results of a number of experiments, in which the plants were 
supplied with more or less of combined nitrogen, in the form of am- 
monia-salts, or of nitrates, are recorded. Ten were with Cereals; 
4in 1857, and 6 in 1858. Three were with Leguminous plants ; and 
there were also some with plants of other descriptions—all in 1858. 
In the case of the cereals more particularly, the growth was very 
greatly increased by the extraneous supply of combined nitrogen ; in 
fact, the amount of vegetable matter produced was 8, 12, and even 
30 times greater than in parallel cases without such supply. The 
amount of nitrogen appropriated was also, in all cases many times 
greater, and in one case more than 30 times as great, when a supply 
of combined nitrogen was provided. The evidence is therefore suffi- 
ciently clear that all the conditions provided, apart from those which 
depended upon a supply of combined nitrogen, were adapted for 
vigorous growth ; and that the limitation of growth where no com- 
bined nitrogen was supplied was due to the want of such supply. 
In 2 out of the 4 experiments with cereals in 1857, there was a 
slight gain of nitrogen beyond that which should occur from error 
in analysis; but in no one of the 6 in 1858, when glazed earthenware 
‘instead of slate stands were used, was there any such gain. It is con- 
‘cluded, therefore, that there was no assimilation of free nitrogen. 
In some cases the supply of combined nitrogen was not given until 
the plants showed signs of decline ; when, on each addition, increased 
vigour was rapidly manifested. In others the supply was given 
earlier and was more liberal. 
As in the case of the Leguminous plants grown without extraneous 
‘supply of combined nitrogen, those grown with it progressed much 
less healthily than the Graminaceous plants. But the results under 
these conditions, so far as*they go, did not indicate any assimilation 
of free nitrogen. 
The results of experiments with plants of other descriptions, in 
which an extraneous supply of combined nitrogen was provided, also 
failed to show an assimilation of free nitrogen. 
Thus, 19 experiments with Graminaceous plants, 9 without and 10 
with an extraneous supply of combined nitrogen—6 with Leguminous 
plants, 3 without and 3 with an extraneous supply of combined 
nitrogen, and also some with other plants, have been made. In 
none of the experiments, with plants so widely different as the 
Graminaceous and the Leguminous, and with a wide range of condi- 
tions of growth, was there evidence of an assimilation of free nitrogen. 
The conclusions from the whole inquiry may be briefly summed 
up as follows :— 7 . 
~* The yield of nitrogen in the vegetation over a given area, within a 
